MongoDB is a document database with the scalability and flexibility that you want with the querying and indexing that you need. – MongoDB website

MongoDB is a NoSQL database, that uses a JSON like schemas and in contrast with relational SQL does not have a predefined data schema.

Data is modeled around object that can easily be queried ad-hoc. MongoDB provides real time aggregation and provides powerful ways to analayze data. MongoDB is a distributed database by design and can be setup for high availability in both vertical scaling and horizontal scaling. MongoDB can be combined with file system access to be used as a real document store.